Drilling fluid tackifier as well as preparation method and application thereof

Abstract

The invention relates to the technical field of drilling fluid treating agents, in particular to a drilling fluid tackifier as well as a preparation method and application thereof. The preparation method comprises the following steps: carrying out a first polymerization reaction by taking modified glucoside and a hydrophobic cross-linking monomer as raw materials to obtain a first polymerization product; and carrying out a second polymerization reaction by taking the first polymerization product, an anionic monomer and a cationic monomer as raw materials to obtain the drilling fluid tackifier. According to the preparation method, the modified glucoside, the hydrophobic cross-linking monomer, the anionic monomer and the cationic monomer are taken as raw materials, the tackifying effect of the drilling fluid tackifier can be effectively improved through the mutual synergistic effect of the monomers, and two polymerization reactions are adopted in the preparation process, so that the polymerization efficiency can be improved, the structure and form of a polymer can be better controlled, and the viscosity of the drilling fluid is improved. Therefore, the performance of the drilling fluid tackifier is improved.

Description

Technical Field

[0001] This invention relates to the field of drilling fluid treatment agents, specifically to a drilling fluid viscosity enhancer, its preparation method, and its application. Background Technology

[0002] Water-in-oil drilling fluids can cool, lubricate, and clean the wellbore during drilling, and stabilize the wellbore. They are the most effective drilling fluids for dealing with highly water-sensitive and complex formations, and also have good anti-collapse properties, making them widely used in unconventional shale oil and gas exploration and development. However, the low mechanical drilling rate and potential safety and environmental problems associated with this type of drilling fluid significantly increase drilling costs and environmental impact.

[0003] EnduraDril water-based drilling fluid is a low-solids, non-dispersed system constructed with brine as the mobile phase, and its performance is comparable to that of traditional oil-based drilling fluids. However, high concentrations of brine, especially high concentrations of divalent brine, have a very adverse effect on polymer hydration, which in turn affects the rheological properties of the drilling fluid.

[0004] In related technologies, one approach is to improve the rheological properties of drilling fluids by developing polymers resistant to high-valent salts. Patent document CN104312549A discloses a high-concentration CaCl2-resistant thickener for water-based drilling fluids, prepared primarily from polyvinyl alcohol, plant gum, and acrylamide monomers. Adding 2% of the thickener to a 25% CaCl2 aqueous solution and undergoing rolling aging, its apparent viscosity at room temperature is 38 mPas, but its temperature resistance is only 120℃. Another approach is to maintain drilling fluid performance by adding specific protective agents. Patent document CN104388064A discloses a calcium chloride water-based drilling fluid system. This system uses 4%–10% methyl glucoside or ethyl glucoside as a protective agent, which can control API filtration loss to within 3.0 mL and high-temperature, high-pressure filtration loss to within 13.0 mL at 120℃ under conditions of 10%–40% CaCl2 concentration. Zhao Hu et al. published an article in the journal *Drilling Fluids and Completion Fluids* on laboratory research of calcium chloride-alkyl glycoside drilling fluid. This article disclosed that when the addition amount of alkyl glycoside was 15%–25%, a drilling fluid with a CaCl2 concentration of 25% could withstand temperatures up to 130℃. However, the above method can only guarantee the drilling fluid's temperature resistance to 120℃–130℃. Summary of the Invention

[0005] This invention provides a drilling fluid viscosity enhancer, its preparation method, and its application, in order to solve the aforementioned problems existing in the prior art.

[0006] According to a first aspect of the present invention, the present invention provides a method for preparing a drilling fluid viscosity enhancer, comprising the following steps: using modified glycosides and hydrophobic crosslinking monomers as raw materials, carrying out a first polymerization reaction to obtain a first polymerization product; Using the first polymerization product, anionic monomer, and cationic monomer as raw materials, a second polymerization reaction is carried out to obtain the drilling fluid viscosity improver.

[0007] The drilling fluid viscosity improver of this invention uses modified glycosides, hydrophobic crosslinking monomers, anionic monomers, and cationic monomers as raw materials. The synergistic effect of these monomers effectively improves the viscosity-enhancing effect of the drilling fluid viscosity improver. Furthermore, the preparation process employs a two-stage polymerization reaction. First, modified glycosides are used as the reaction substrate to undergo a first polymerization reaction with the hydrophobic crosslinking monomers to obtain the first polymerization product. Then, the first polymerization product is subjected to a second polymerization reaction with the anionic and cationic monomers. This process improves polymerization efficiency, allows for better control of the polymer structure and morphology, and thus enhances the performance of the drilling fluid viscosity improver. The drilling fluid viscosity improver prepared by this method exhibits excellent performance. After rolling aging at 150°C for 16 hours in a bentonite-based slurry containing 30% CaCl2 (by mass / volume), the apparent viscosity retention rate reaches over 75%.

[0008] Furthermore, the modified glycoside is prepared by reacting the glycoside, inorganic base, and haloalkene in water. This invention, by modifying the glycoside and introducing unsaturated double bonds into the original glycoside molecular structure, can effectively increase the polymerization efficiency of the monomer, improve the molecular weight of the drilling fluid thickener, and thus enhance the thickening performance of the drilling fluid thickener.

[0009] Furthermore, the temperature of the modification reaction is 40℃~80℃. By controlling the temperature of the modification reaction, the efficiency of the modification reaction can be improved, and the performance of the modified glycosides can be enhanced.

[0010] Furthermore, in the modification reaction, the mass ratio of glycoside to haloalkene is (1-2):(0.1-0.5). By controlling the ratio of each raw material in the modification reaction, the efficiency of the modification reaction can be improved, and the performance of the modified glycoside can be enhanced.

[0011] Furthermore, in the modification reaction, the mass ratio of glycoside, inorganic base, water, and haloalkene is (1-2):(0.1-0.5):(0.1-0.5):(0.1-0.5). By controlling the ratio of each raw material in the modification reaction, the efficiency of the modification reaction can be improved, and the performance of the modified glycoside can be enhanced.

[0012] Furthermore, the glycoside is one or more of nonionic alkyl glycosides and cationic alkyl polysaccharides. By selecting a suitable type of glycoside, the performance of the modified glycoside can be improved.

[0013] Furthermore, the inorganic base is one or more of potassium hydroxide, sodium hydroxide, calcium hydroxide, magnesium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, and magnesium carbonate, preferably one or two of sodium hydroxide and potassium hydroxide.

[0014] Furthermore, the haloolefin is one or more of allyl chloride, chloroprene, bromopropylene, and 1-bromo-2-butene. By selecting a suitable type of haloolefin, the performance of the modified glycoside can be improved, which is beneficial for subsequent polymerization reactions with other monomers and improves the performance of drilling fluid viscosity improvers.

[0015] Furthermore, the modified glycoside is prepared by reacting the glycoside, inorganic base, and haloalkene in water followed by dehydration. Dehydration is a conventional method in the art, and can be achieved through a water separator, solvent extraction, or distillation.

[0016] Furthermore, the hydrophobic crosslinking monomer is one or both of divinylbenzene and 1,3-diisopropenylbenzene. These monomers can form better synergistic effects with the modified glycosides, anionic monomers, and cationic monomers used in this invention, thereby improving polymerization efficiency and enhancing the performance of drilling fluid thickeners.

[0017] Furthermore, the anionic monomer is one or more selected from styrene sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and 2-acrylamido-dodecanesulfonic acid. These monomers can form better synergistic effects with the modified glycosides, hydrophobic crosslinking monomers, and cationic monomers used in this invention, thereby improving polymerization efficiency and enhancing the performance of drilling fluid viscosity improvers.

[0018] Furthermore, the cationic monomer is one or more of N-vinylformamide, methacrylamidopropyltrimethylammonium chloride, and diallyldimethylammonium chloride. These monomers can form better synergistic effects with the modified glycosides, hydrophobic crosslinking monomers, and anionic monomers used in this invention, thereby improving polymerization efficiency and enhancing the performance of drilling fluid thickeners.

[0019] Furthermore, the first polymerization reaction specifically includes the following steps: The modified glycoside, hydrophobic crosslinking monomer, first initiator and water were emulsified at 3000-6000 r / min for 10-15 min to obtain a mixture; The obtained mixture was reacted at a stirring speed of 200-300 r / min and a temperature of 50-60℃ for 3-5 h to obtain the first polymerization product. By optimizing the process conditions of the first polymerization reaction, the efficiency of the first polymerization reaction can be improved, which in turn facilitates the subsequent second polymerization reaction.

[0020] Preferably, the mass ratio of the hydrophobic crosslinking monomer, the modified glycoside, and the first initiator is (1-3):(10-15):(0.1-0.2).

[0021] Preferably, the mass ratio of the hydrophobic crosslinking monomer, the modified glycoside, the first initiator, and water is (1-3):(10-15):(0.1-0.2):(40-50); the first initiator is one of ammonium persulfate, potassium persulfate, and cerium ammonium nitrate.

[0022] Furthermore, the second polymerization reaction is carried out in water using the first polymerization product, anionic monomers, and cationic monomers as raw materials under the action of a second initiator.

[0023] Preferably, the second polymerization reaction is carried out by first maintaining the temperature at 70-80°C and the stirring speed at 200-300 r / min for 0.5-1 h; then stopping the stirring and continuing the reaction at the same temperature for 5-7 h. By optimizing the process conditions of the second polymerization reaction, the efficiency of the secondary polymerization reaction can be improved, thereby obtaining a polymer with an ideal molecular structure and improving the performance of the drilling fluid viscosity improver.

[0024] Furthermore, in the second polymerization reaction, the mass ratio of anionic monomer, cationic monomer, and second initiator is (3-5):(1-3):(0.3-0.5).

[0025] Furthermore, in the second polymerization reaction, the mass ratio of anionic monomer, cationic monomer, second initiator and water is (3-5):(1-3):(0.3-0.5):(15-25); preferably, the second initiator is ammonium persulfate or potassium persulfate.

[0026] According to a second aspect of the present invention, the present invention provides a drilling fluid viscosity improver prepared by the above-described preparation method.

[0027] The drilling fluid viscosity enhancer of this invention comprises cationic groups, anionic groups, and hydration groups in its molecular structure, and is an amphiphilic polymer with rigid polymer chains. This polymer adsorbs onto the surface of hydrated clay particles through electrostatic and hydrogen bonding interactions, utilizing the hydrophobic association effect in its molecular structure and the attraction of cationic groups to Ca... 2+ The electrostatic repulsion of ions resists high concentrations of Ca. 2+ It dehydrates clay particles, improving the stability of brine-based drilling fluids under high-temperature (above 150℃) conditions.

[0028] Furthermore, the drilling fluid viscosity enhancer has a weight-average molecular weight of 5 to 5.5 million. A drilling fluid viscosity enhancer with this molecular weight exhibits excellent viscosity-enhancing properties, thereby improving the stability of the drilling fluid.

[0029] According to a third aspect of the invention, the invention also provides the application of the above-described drilling fluid viscosifier in drilling fluids. A drilling fluid includes the drilling fluid viscosifier prepared by the above-described preparation method or the above-described drilling fluid viscosifier.

[0030] The beneficial effects of this invention are: The drilling fluid viscosity enhancer provided by this invention comprises cationic groups, anionic groups, and hydration groups, and is an amphiphilic polymer with rigid polymer chains. This polymer adsorbs onto the surface of hydrated clay particles through electrostatic and hydrogen bonding interactions, utilizing the hydrophobic association effect in its molecular structure and the attraction of cationic groups to Ca... 2+ The electrostatic repulsion of ions resists high concentrations of Ca. 2+ It dehydrates clay particles, improving the stability of brine-based drilling fluids under high-temperature conditions.

[0031] This invention provides a method for preparing a drilling fluid viscosity improver using modified glycosides, hydrophobic crosslinking monomers, anionic monomers, and cationic monomers as raw materials. The synergistic effect of these monomers effectively improves the viscosity-enhancing effect of the drilling fluid viscosity improver. Furthermore, the preparation process employs a two-stage polymerization reaction, which improves polymerization efficiency and allows for better control of the polymer structure and morphology, thereby enhancing the performance of the drilling fluid viscosity improver. The drilling fluid viscosity improver prepared by this method exhibits excellent performance; after rolling aging at 150°C for 16 hours in a bentonite-based slurry containing 30% CaCl2 (by mass), the apparent viscosity retention rate reaches over 75%. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] Example 1 This embodiment provides a drilling fluid viscosity enhancer, the preparation method of which includes the following steps: Take 50g of alkyl glycoside 0810, 5g of sodium hydroxide, and 5g of water, mix them thoroughly, heat to 50℃, and slowly add 5g of allyl chloride dropwise. After the addition is complete, continue the reaction for 1 hour, and then use a water separator to dehydrate to obtain the modified glycoside.

[0034] 1g divinylbenzene, 10g modified glycoside, 0.1g potassium persulfate, and 50g deionized water were placed in a shear emulsification apparatus and emulsified at 4000 rpm for 20 min to obtain a mixed emulsion. The above mixed emulsion was transferred to an open reactor equipped with a temperature control device and a nitrogen purging device. The temperature was set at 60℃, the stirring speed at 200-300 rpm, and the reaction was maintained at this temperature for 3-5 h to obtain a viscous substance. 3g 2-acrylamido-2-methylpropanesulfonic acid, 1g methacrylamidopropyltrimethylammonium chloride, 0.3g potassium persulfate, and 15g deionized water were placed in a beaker and thoroughly mixed and dissolved. The obtained mixture was placed in the above viscous substance and mixed. The temperature was adjusted to 70°C, the stirring speed was 200 r / min, and the reaction was kept at this temperature for 0.5 h. After stirring was stopped, the reaction was kept at this temperature for another 5 h to obtain a gel. The gel was taken out of the reaction vessel, dried at 60°C for 8 h and then pulverized to obtain a white powder product, which is the high-temperature resistant water-based drilling fluid thickener of this embodiment.

[0035] Example 2 This embodiment provides a drilling fluid viscosity enhancer, the preparation method of which includes the following steps: Take 50g of alkyl glycoside 0810, 5g of potassium hydroxide, and 5g of water, mix them thoroughly, heat to 50℃, and slowly add 5g of allyl bromide dropwise. After the addition is complete, continue the reaction for 1 hour, and then use a water separator to dehydrate to obtain the modified glycoside. 1g divinylbenzene, 10g modified glycoside, 0.1g potassium persulfate, and 50g deionized water were placed in a shear emulsification apparatus and emulsified at 4000 rpm for 20 min to obtain a mixed emulsion. The above mixed emulsion was transferred to an open reactor equipped with a temperature control device and a nitrogen purging device. The temperature was set at 60℃, the stirring speed at 200-300 rpm, and the reaction was maintained at this temperature for 3-5 h to obtain a viscous substance. 3g 2-acrylamido-2-methylpropanesulfonic acid, 1g methacrylamidopropyltrimethylammonium chloride, 0.3g potassium persulfate, and 15g deionized water were placed in a beaker and thoroughly mixed and dissolved. The obtained mixture was placed in the above viscous substance and mixed. The temperature was adjusted to 70°C, the stirring speed was 200 r / min, and the reaction was kept at the temperature for 0.5 h. After stirring was stopped, the reaction was kept at the temperature for another 5 h to obtain a gel. The gel was taken out of the reaction vessel, dried at 60°C for 8 h and then pulverized to obtain a white powder product, which is the high-temperature resistant water-based drilling fluid thickener of the present invention.

[0036] Example 3 This embodiment provides a drilling fluid viscosity enhancer, the preparation method of which includes the following steps: Take 50g of alkyl glycoside 0810, 5g of sodium hydroxide, and 5g of water, mix them thoroughly, heat to 50℃, and slowly add 5g of allyl chloride dropwise. After the addition is complete, continue the reaction for 1 hour, and then use a water separator to dehydrate to obtain the modified glycoside. 1 g of 1,3-diisopropenylbenzene, 10 g of modified glycoside, 0.1 g of potassium persulfate, and 50 g of deionized water were placed in a shear emulsification apparatus and emulsified at 4000 r / min for 20 min to obtain a mixed emulsion. The above mixed emulsion was transferred to an open reactor equipped with a temperature control device and a nitrogen purging device. The temperature was set at 60℃, the stirring speed at 200-300 r / min, and the reaction was maintained at this temperature for 3-5 h to obtain a viscous substance. 3 g of 2-acrylamido-2-methylpropanesulfonic acid, 1 g of methacrylamidopropyltrimethylammonium chloride, 0.3 g of potassium persulfate, and 15 g of deionized water were placed in a beaker and thoroughly mixed and dissolved. The obtained mixture was placed in the above viscous substance and mixed. The temperature was adjusted to 70°C, the stirring speed was 200 r / min, and the reaction was kept at the temperature for 0.5 h. After stirring was stopped, the reaction was kept at the temperature for another 5 h to obtain a gel. The gel was taken out of the reaction vessel, dried at 60°C for 8 h and then pulverized to obtain a white powder product, which is the high-temperature resistant water-based drilling fluid thickener of the present invention.

[0037] Example 4 This embodiment provides a drilling fluid viscosity enhancer and its preparation method. The difference from Embodiment 1 is that the preparation method of the modified glycoside is different. Specifically, the mass ratio of alkyl glycoside 0810, inorganic base, water and halogenated olefin is 2:0.1:0.1:0.1.

[0038] Example 5 This embodiment provides a drilling fluid viscosity enhancer and its preparation method, which differs from Embodiment 1 in that the anionic monomer is different, specifically 2-acrylamidododecanesulfonic acid.

[0039] Example 6 This embodiment provides a drilling fluid viscosity enhancer and its preparation method, which differs from Embodiment 1 in that the cationic monomer is different, specifically diallyl dimethyl ammonium chloride.

[0040] Example 7 This embodiment provides a drilling fluid viscosity enhancer and its preparation method, which differs from Embodiment 1 in that: during the first polymerization reaction, the mass ratio of modified glycoside, hydrophobic crosslinking monomer, first initiator and water is 15:1:0.1:50.

[0041] Comparative Example 1 This comparative example provides a drilling fluid viscosity enhancer, the preparation method of which differs from that of Example 1 in that: no alkyl glycoside is modified, and the alkyl glycoside is directly used to replace the modified glycoside in subsequent reactions.

[0042] Comparative Example 2 This comparative example provides a drilling fluid viscosity enhancer, the preparation method of which differs from that of Example 1 in that the viscosity enhancer is prepared by a single polymerization reaction, the specific process of which is as follows: Take 50g of alkyl glycoside 0810, 5g of sodium hydroxide, and 5g of water, mix them thoroughly, heat to 50℃, and slowly add 5g of allyl chloride dropwise. After the addition is complete, continue the reaction for 1 hour, and then use a water separator to dehydrate to obtain the modified glycoside.

[0043] 1g of divinylbenzene, 10g of modified glycoside, and 50g of deionized water were placed in a shear emulsification apparatus and emulsified at 4000r / min for 20min to obtain a mixed emulsion. 3g of 2-acrylamido-2-methylpropanesulfonic acid, 1g of methacrylamidopropyltrimethylammonium chloride, 0.4g of potassium persulfate, and 15g of deionized water were placed in a beaker and thoroughly mixed and dissolved. The resulting mixture was then mixed with the above mixed emulsion and transferred to an open reactor equipped with a temperature control device and a nitrogen purging device. The temperature was set at 70℃, the stirring speed at 200-300r / min, and the reaction was maintained at this temperature for 3-5h to obtain a gel-like substance. The gel-like substance was removed from the reactor, dried at 60℃ with forced air for 8h, and then pulverized to obtain a white powdery product, which is the anti-drilling fluid thickener of this comparative example.

[0044] The weight-average molecular weight of the drilling fluid viscosifiers in the examples and comparative examples was determined by gel permeation chromatography. Sodium nitrate solution was used as the mobile phase at a flow rate of 0.5 mL / min, and the test temperature was 30 °C. The results are shown in Table 1 below.

[0045] Table 1 Weight-average molecular weight of drilling fluid viscosifiers weight average molecular weight Example 1 5.2 million Example 2 5 million Example 3 5.3 million Example 4 5.22 million Example 5 5.38 million Example 6 5.16 million Example 7 5.28 million Comparative Example 1 3.2 million Comparative Example 2 3.15 million

[0046] Performance test base slurry preparation: Add 40g bentonite and 5g Na2CO3 to 1000mL of water, stir at 100r / min for 2h, and cure at room temperature for 24h to obtain fresh water base slurry.

[0047] Apparent viscosity test: Take 400 mL of the above-mentioned fresh water-based slurry, add 3% synthetic thickener at a stirring speed of 3000-6000 r / min, stir for 20 min, then add 120 g CaCl2, continue stirring for 20 min, and then measure the apparent viscosity using a six-speed viscometer. After aging at 150℃ for 16 h, measure the apparent viscosity again using a six-speed viscometer.

[0048] Table 2 shows the viscosity test results of the drilling fluid viscosifiers in the examples and comparative examples before and after aging in 30% CaCl2 brine-based slurry.

[0049] Table 2. Apparent viscosity test results of brine-based slurry containing 30% CaCl2 before and after aging at 150℃.

[0050] The results in Table 2 show that the brine-based drilling fluid thickener obtained by the preparation method described in this invention can maintain the apparent viscosity of the brine-based slurry in 30% CaCl2 brine-based slurry up to 75% before and after aging at 150°C.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a drilling fluid viscosity improver, characterized in that, Includes the following steps: Using modified glycosides and hydrophobic crosslinking monomers as raw materials, a first polymerization reaction was carried out to obtain the first polymerization product; Using the first polymerization product, anionic monomer, and cationic monomer as raw materials, a second polymerization reaction is carried out to obtain the drilling fluid viscosity improver.

2. The preparation method according to claim 1, characterized in that, The modified glycoside is prepared by reacting the glycoside, inorganic base, and haloalkene in water.

3. The preparation method according to claim 2, characterized in that, In the modification reaction, the mass ratio of glycoside to haloalkene is (1-2):(0.1-0.5); Preferably, the haloolefin is one or more of chloropropene, chloroprene, bromopropene, and 1-bromo-2-butene.

4. The preparation method according to any one of claims 1-3, characterized in that, The hydrophobic crosslinking monomer is one or both of divinylbenzene and 1,3-diisopropenylbenzene; And / or, the anionic monomer is one or more of styrene sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and 2-acrylamido-dodecanesulfonic acid; And / or, the cationic monomer is one or more of N-vinylformamide, methacrylamidopropyltrimethylammonium chloride, and diallyldimethylammonium chloride.

5. The preparation method according to any one of claims 1-4, characterized in that, The first polymerization reaction specifically includes the following steps: The modified glycoside, hydrophobic crosslinking monomer, first initiator and water were emulsified at 3000-6000 r / min for 10-15 min to obtain a mixture; The obtained mixture was reacted at a stirring speed of 200-300 r / min and a temperature of 50-60℃ for 3-5 h to obtain the first polymerization product.

6. The preparation method according to claim 5, characterized in that, The mass ratio of the hydrophobic crosslinking monomer, the modified glycoside, and the first initiator is (1-3):(10-15):(0.1-0.2).

7. The preparation method according to claim 1, characterized in that, The second polymerization reaction is carried out in water using the first polymerization product, anionic monomers and cationic monomers as raw materials under the action of a second initiator. Preferably, the second polymerization reaction is carried out by first maintaining the temperature at 70-80°C and stirring at 200-300 r / min for 0.5-1 h; then stopping the stirring and continuing the reaction at the temperature for 5-7 h.

8. The preparation method according to claim 7, characterized in that, The mass ratio of the anionic monomer, the cationic monomer, and the second initiator is (3-5):(1-3):(0.3-0.5).

9. A drilling fluid viscosity improver, characterized in that, Prepared by the preparation method according to any one of claims 1-8; The drilling fluid viscosity enhancer has a weight-average molecular weight of 5 million to 5.5 million.

10. A drilling fluid, characterized in that, This includes drilling fluid viscosity enhancers prepared by any one of the preparation methods described in claims 1-8 or the drilling fluid viscosity enhancer described in claim 9.

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